Why do some people sneeze when they look at the sun?

Have you ever stepped out of a dim subway station into the sunshine and felt that telltale tickle in your nose—the unmistakable need to sneeze? Sneezing in the sudden presence of bright light, especially sunlight, is a phenomenon known as sun sneezing or the photic sneeze reflex. It affects anywhere between 10 to 35 percent of the population, depending on which survey you read. A 1987 study in the Cleveland Clinic Journal of Medicine, for example, estimated its prevalence at 17 to 35 percent of the population. A 1983 study in Human Heredity found a 24 percent prevalence among 460 blood donors.

Although most of us aren’t sun sneezers, it’s a common enough curiosity to get lots of people wondering: What’s going on here?

There’s still no hard evidence to fully explain sun sneezing, but scientific and popular attention has largely focused on a particular hypothesis proposed in 1964 by Henry Everett when he was a psychiatrist at Johns Hopkins University Hospital. According to the hypothesis, the photic sneeze reflex is caused by a confusion of nerve signals in pathways very near one another. Since sneezing is such a sudden and involuntary reflex, the cause is probably located in the nervous system, which is capable of transmitting signals very quickly.

Researchers suspect that two important reflexes may play a key role in sun sneezing. The first is the pupillary light reflex. In this reflex, bright light entering the eyes sends signals along the optic nerve to the brain, which sends signals back to the eyes to constrict the pupils—a means of adjusting to differently lit environments. The second is the sneeze reflex, in which a cranial nerve called the trigeminal nerve detects a tickling in the nose and alerts the brain, which in turn stimulates the chest, nose, mouth and other muscles involved in sneezing.

For most of us, the pathways involved in these two reflexes—though physically close—do not directly interact. But in sun sneezers, the hypothesis claims, one pathway stimulates the other. The result? Exposure to bright light sends a signal to the brain to constrict the pupils, as usual, but the crossed wires rouse a sneeze as well. “While this is an interesting hypothesis, there’s no data supporting it or any other hypothesis for that matter,” said Louis Ptácek via email. Ptácek is a neurologist at the University of California, San Francisco who studies the photic sneeze reflex.

An alternative hypothesis attempts to explain sun sneezing and other strange sneezing behaviors by singling out the medulla oblongata, a part of the brainstem that helps regulate many involuntary processes, including breathing, heart rate and sneezing. Believe it or not, some people always sneeze after eating a large meal—a condition called snatiation—while others sneeze during orgasm. Constriction of the pupils, the feeling of being stuffed, and orgasm are exactly the kind of reflexes mediated by the medulla. The implication is that, for some individuals, all these signals flowing to the same area of the brainstem might be getting a bit mixed up.

The specific genes responsible for sun sneezing have not yet been identified, but scientists can guess your chances of having the photic sneeze reflex because of the way it’s inherited—it’s an autosomal dominant trait. This means that if just one of your parents has one copy of the culprit gene, you have a 50 percent chance of being a sun sneezer. In 1978, a group of witty eggheads pounced on the new genetic evidence as an opportunity to create the following acronym for the photic sneeze reflex: Autosomal-dominant Compelling Helio-Ophthalmic Outburst syndrome—ACHOO!

Although most sun sneezers accept their condition as an odd but harmless quirk, there’s been plenty of speculation about harmful consequences. According to a 1993 issue of Military Medicine, sun sneezing could threaten combat pilots by interfering with their vision, leading to potentially fatal situations. Similar fears have been raised about drivers emerging from dark tunnels into bright light. Some researchers have even expressed concerns over baseball players searching the sunny skies for a fly ball.

So much for the gloom and doom. Are there any benefits to the photic sneeze reflex—anything at all? Some have theorized that sun sneezing is a gift of evolution, passed down from our cavemen forefathers. According to the theory, after hanging out in dark, dirty caves all day, our ancestors’ noses and throats would become full of dust and need a little forceful cleaning. When the cavemen emerged from their dwellings into the sun, they would sneeze, thereby clearing their noses and throats of cave must. Unfortunately, this theory is an old wives’ tale, about as verifiable as the Area 51 conspiracy.

The photic sneeze reflex has largely eluded our attempts to understand it, remaining a mystery for neuroscientists and sun sneezers alike. “There is so little known about the photic sneeze reflex that I think the jury is completely out at this point,” said Ptácek.

Sun sneezing is, however, becoming more well known. The photic sneeze reflex recently attracted the attention of 23andMe, a company that will analyze the DNA in your saliva to predict your chances of having certain heritable traits and diseases. Sun sneezing also found its way into the popular Berenstain Bears series of children’s books. And anecdotal evidence suggests that some people take advantage of the reflex, training themselves to hasten an imminent sneeze by directing their attention to the sun. There’s even an online support group for those with the photic sneeze reflex.

If you would like to help scientists specify the genetic factors involved in sun sneezing, you can apply to participate in ongoing research at the University of California, San Francisco, where Ptácek and his colleagues work. “We’ve collected some interesting families,” Ptácek said, but they will need many more volunteers before they find something conclusive.

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Both my husband and I are sun sneezers…only to the effect that we can help ‘push’ a sneeze along by looking up at the sky. Our little daughter however is a full-on sun sneezer. She will sneeze every time she goes out in to the sun and then periodically if we stay outside. She has the talent of being able to ‘make’ herself sneeze simply by looking up at the sky…she can usually only do it once though. It’s very helpful when she has a stuffy nose…i say, lets go outside and sneeze…loosens up that snot quite quickly

I found everyone’s input on this subject was interesting and inquisitive. I don’t think the people on here calling people dumb etc. are very educated either for they should know the rule of thumb that no question is a stupid one. It is an attempt to gain knowledge. Sorry for all this but after I read the comments that were put downs, I found them very rude.

i am a person who has photic sneeze reflex and yes i use this as an advantage to get rid of a sudden urge to sneeze while i am exposed out in the sun. this passage i thought was very helpful i thought that this was a trait that all human beings shared, but turns out only select individuals depending on their genetic traits passed down from generations have photic sneeze reflex.

I guess iam suffering photic sneeze reflect but i dont like its abit…i sneeze every morning 8 to 10 time and its cause me painful around my hold body,sometime even my tear come out unable to bear the sneeze i guess..and after the sneeze end i find my nose watery and even inside my nose its like something inside its and make me feel iritating..but it only happen in everytime i wake up and go for a brush its has no fixed time and all the symtom or problem end after an hours

Really enjoyed the article and discussion. My husband and I just had our first daughter 2 months ago and her morning/after nap sneezes had reawakened the sun sneeze debate in our house. Hubs has always thought me nuts for believing that bright sunlight makes me sneeze. Especially when we were sharing a car for a while, we’d take a turn toward the highway each morning and like clockwork (on a sunny morning that the windshield gets flooded) I’d sneeze. I remember my blue eyed mom trying to explain to me when I was little, that it was because of mu light green eyes (and why my blue eyed sister also sneezed with sunlight and my brown eyed dad, sister, and brother didn’t). Now my blue eyed (so far) daughter and I carry on this oddity and keep my husband delightfully puzzled.

I’m 17 at the moment and every time I look at the sun I sneeze. It’s been that way for as long as I can remember. Even now I’ve started to sneeze every time I eat any kind of food at every meal I have. Never really gave much thought to any of it tbh.

Well, that’s odd. I only sneeze when I simply step into sunlight, but it is specifically when I’m outside, and is daytime. If I go outside at night, I won’t sneeze. Bright light doesn’t make me sneeze either, so I feel like this article really didn’t explain what is going on with me.

As yet another sufferer i also have speculated about the cause. I cannot speak for others but bright lights besides the sun do not affect me…. it makes me wonder if perhaps the sneeze is a built in defense mechanism. We are now only too aware of the suns damaging rays…when we sneeze we generally look down…but it definately forces us to close our eyes…perhaps its your body telling you to look away from the sun.

I also Suffer from this odd condition but I have noticed it is any change in light patterns. For instance if a glare from chrome or a bright light off glass is reflected at me I will sneeze usually several times in a row. It does not have to be sunlight. I have even been able to catch myself and slow the process down but my eyes still water quickly. I hope they will research this it would be nice to know what else is linked to this condition.

This is interesting because i wake up fine and then when i go down the stairs and open up curtains to my back garden im usually blinded by the light esl in the spribg/summer and i end up sneezing three to four times before i even move from the window

This is so weird and would explain why when i get up to open the curtains in my living room particulary on a sunny day, im blinded for a seccond and before i get chance to move from the window i sucumb to a sneeze, or more until i move from the window

I always sneeze when I look at the sun ,maybe 2 to 3 times ,my brother too and now his son also,we all have blue eyes,and wondered if this could be the reason,I also think this could just be a natural defence system from your body,because what do you do when you sneeze? you close your eyes!

My bird is actually the one who is the sun sneezer! Oddly enough, he is a sun conure who we always giggled about being allergic to the sun, because when a sun bean hits him he sneezes! Someone just pointed out to me that it was a human thing too.

This happened to me occasionally when I was younger. I’m 37 now, kinda wondering why it doesn’t happen anymore. I think now I usually close my eyes as soon as the sun hits me so that they adjust slowly. I also do the one eye open technique until it adjusts then open the other. Btw. My eyes are brown.

… maybe in some people their eyes don’t adjust fast enough so to protect the eyes from the sun the sneeze reflex is triggered and the eyes close which gives pupils time to adjust. Maybe, like other parts of the body, sneezing makes the pupils contract faster.

I am also a photic sneezer. I think it’s a handy trick but I guess I don’t have some of the problems others do. If I have a sneeze stuck I can look into a bright light, like a lamp with a 60 watt bulb in it and make myself sneeze and that takes care of it. For light to make me sneeze if I’m not even close to sneezing it has to be a situation like having gone to a matinee and sat in a dark theater and walk out directly into the sun. Up until recently I also thought it was something everyone could do.

My son and I are sun sneezers. We love it. I let him know that we have the special ability to make ourselves sneeze when we want and most other people cannot do it. I have known that I was different from other since I was in 3rd grade when other kids would say things like “I have to sneeze and cannot”. A couple of us would tell them to go into the sun and look up. They couldn’t do it.

I think I have always been a sun sneezer but never really thought anything about it. Sunlight or bright lights alone don’t make me sneeze but if I look up near the sun I will start sneezing. Now I find out that only a certain percentage of people are affected by this condition that I thought every one had.

I have this blessing, it used to be so disappointing when you get that feeling of a sneeze coming on and it just sort of fizzles out, then I learned that if I just look up into the light it’ll come straight out and the world is good again.
I’ve just had this happen today where I was about to lose it but caught the light just in time, hence me googling it and finding this very informative article. Thank you!

At age 62, I can remember being a sun sneezer my entire life. I’ve never really understood it until recently, and it seems, no one else understands the medical side of it either. No big deal…never has been. I usually only sneeze when emerging from a dark place into the sunlight, and then not every time. When I do sneeze, it’s usually three times that my wife takes great delight in counting off for those in attendance. I guess it makes her feel that she appears to be clairvoyant. LOL !! I will say this however, I’ve never met another person that has this condition…at least it’s not been revealed or discussed. Makes me feel special :).

I share many of the experiences discussed here and it’s nice to know I’m not alone in the crazy sneezing world. Best wishes to all my fellow sneezers out there !!

I have the same issue but not too bad
I only sneeze after being inside for a long time or walking around a store for a good bit, and it’s only ever one sneeze. Strange but feeling better knowing there are more like me out there haha!

I am 38 and I’ve been a sun sneezer as long as I can remember, but artificial light can make me sneeze too. Like others have mentioned, if I have a sneeze that won’t come out I just have to look out the window near the sun, a lamp or anything bright and voila. I thought for the longest time that everyone could experience this. While working in the oil field, the guy that drove the crew truck would sneeze at the same place as we came over the crest of a hill each evening (sometimes me too but I could look away, as I wasn’t driving)and it got the four of us talking about it. The other two guys weren’t sun sneezers and it was then that I realized it is not that common. Not that it comes up that often, but I have only met a few other confirmed sun sneezers. I like it!

I am sixteen almost seventeen and I was actually kinda scared I had a problem. I never researched it until now and I figured out it wasn’t just me a bit ago in someones commentary i watched. I’m glad I found this it put all my worries away. I’ve noticed it sense I was around 9 and at random times in the sun I either have a sudden need to sneeze or do sneeze. But I am no matter what sneezing if I look up on a sunny day.

I sneeze a lot anyway and the sun always sets me off! I am very photosensitive too – need to wear sunglasses on any sunny day. I had hayfever severely as a child but it subsided by my early 20s. It is only now at 66 I realise I am odd to sneeze so frequently,repeatedly and loudly in the sun!

I never knew there was a clinical term for sun sneezing, thus I googled it. I am 46. I sneeze when I go outside. Would love to find out more. To know studying DNA and family history sounds intriguing. I never asked my family about this. I don’t have allergies.

Growing up, if we went outside without sunglasses on and sneezed, my mother would never say “bless you”, she would simply say “I told you to wear sunglasses”. It wasn’t until I was in my mid twenties that I realized not everyone had this issue. If someone would say “I can’t sneeze” I would tell them to look into a bright light or the sun and the sneeze would come out. I would always get a very weird look before the person tried it, but their sneeze would never come out. After getting a few of those weird looks, I realized that people don’t sneeze with bright lights. Now, I catch myself from telling people to look in the bright light to bring out the sneeze, because it is not normal. I love that I can just look into the bright light (sun or light bulb), I never get a stuck sneeze.

As a young boy, I knew that direct sunlight caused me to sneeze. I recall my mother scoffing at the idea when I mentioned it to her. Obviously, she didn’t have the gene I have. I now know that this effect is also often induced after an orgasm and when I eat too much too fast.

My friend bought me a desk lamp. I have never in my life had a lamp that was so good at getting my sneezes out. Like some of the others here have mentioned I can sneeze just as easily from indoor artificial light as from the sun outside. I too never knew until today that maybe only 25% of the population has this ability. I have brown eyes. I’ve been sun sneezing since at least 7 or 8 years old.

I am the only one in my immediate family that is a sun sneezer. My mother has told me that I’ve been doing it since I was a baby. Now my nephew is a sun sneezer, but neither of his parents is. I also can use artificial light to induce a sneeze if it’s “stuck.” My family and friends know that if I say, “Hold on…,” and look at the sun or a light, that I’m going to sneeze. They all think it’s pretty funny. I’m a redhead, and only 1 – 2% of the population has red hair. I wonder what percentage also sun sneeze. I may really be a rare breed! :)

I noticed that every day when i go outside as soon as the sun hits my face i have uncontrollable sneezing. I can sneeze 10 or more times back to back. My eyes start running. Sometimes my nose. Also whenever i awake from sleeping if I don’t open my eyes ill be fine. As soon as i look at my cell phone to see the time and the light shines on my eyes that triggers the repetitive sneezing. I just decided to google this to see if the sneezing could actually be connected to the light as I suspected, so im happy to see that others experience this because others don’t understand when i tell them.

I have always dealt with this. Upon walking outside, when the clouds part to expose the sun, etc. I can be looking at the ground. My 2 kids have it too.
Now whats interesting is they talk about the trigeminal nerve. I was recently diagnosed with Trigeminal Neuralgia and havnt experienced sun sneezing since.

I have this reflex! But I feel that my sun-sneezes are noticeably different from actual sneezes (when i’m sick, or having allergies). They’re mostly dry (there’s no secretion to be expelled from my nose!) and I can hold them in for several seconds, although the feeling of needing to sneeze happens immediately as I walk into a brightly-lit space.
I wonder if this gene has something to do with photophobia, too. If I try to hold a “sun-sneeze” for too long, my eyes will want to close on their own! And a guy I met who suffered from photophobia was also a sun-sneezer. Perhaps they’re different genes that reinforce each other?!